Kilroy Realty Corp. is ready to build at 333 Brannan St. — but don’t be surprised if the group lands a tenant before contractor Swinerton finishes excavation.

The real estate investment trust, which since 2010 has pumped more than $2 billion into San Francisco real estate, held the ceremonial groundbreaking Dec. 19 for the $95 million, 170,000-square-foot development in the heart of the South of Market district. The brick and concrete building will replace a surface parking lot which Mayor Ed Lee said was notable primarily as the traditional home to the San Francisco Fire Department’s annual chili cook-off.

Companies circling the project include Pinterest, Dropbox and LinkedIn. With a dozen prominent commercial real estate brokers in attendance, even Mayor Lee sensed that a deal was close.